Known disk drive units include those which use a variety of recording disks such as optical disk, magneto-optical disk, and flexible magnetic disk. The most popular among them is the hard disk drive (HDD) which is widely used as the indispensable memory unit for present-day computer systems. Because of its outstanding characteristics, the HDD is finding new uses as removable memory in many areas other than computers, such as animation recording and playback, car navigation systems, mobile phones, and digital cameras.
The magnetic disk used for the HDD has many concentric data tracks, each having data sectors containing servo data (for address information) and user data. The data sector is accessed by the head element according to the address information contained in the servo data, so that it permits data writing and reading.
The head element is mounted on the slider which is fixed to the suspension of the actuator. The assembly consisting of the actuator and the head slider is called the head stack assembly (HSA). Also, the assembly consisting of the suspension and the head slider is called the head gimbal assembly (HGA).
The head slider floats above the magnetic disk with a certain gap between them owing to a balance between two forces, one generated by the viscosity of air between the rotating magnetic disk and the air bearing surface (ABS) of the slider facing the magnetic disk, and the other toward the magnetic disk generated by the suspension. The suspension has the gimbal, which holds the head slider opposite to the magnetic disk, and the load beam which holds the gimbal opposite to the magnetic disk. The gimbal is capable of deformation so that the slider can sway in prescribed directions to follow the vibration of the magnetic disk.
The suspension is also provided with a limiter mechanism which limits the gap between the gimbal and the load beam so that the gimbal will not deform excessively. An example of the limiter mechanism is disclosed in Japanese Laid-Open Patent No. 2004-134059.
As mentioned above, the suspension should be provided with the limiter mechanism to limit the deformation of the gimbal for its effective function. On the other hand, more difficulties than before are involved in the design of the gimbal as the recording density of the magnetic disk increases and the floating height of the head decreases. It is necessary for the gimbal to follow the lengthwise and lateral movements of the head slider so that the head slider can move smoothly.
On the other hand, the gimbal also needs strength. It should be strong enough to move the head slider away from the magnetic disk in the case of HDD of load-unload type. For the gimbal to have an adequately designed shape, the parts around the head slider should be designed more freely than before.